Thread necro because unsolved - Was there ever a solution for this?
There is another earlier thread about the same issue, noting that it should only be affecting the web client - and I am definitely seeing this error when attempting to browse an FTP via the web, but also getting the same error on the desktop client.
The FTP server in question is a gameserver that uses only plain FTP (no TLS/etc), although I am able to connect to it via MultCloud’s FTP interface just fine - as a current workaround, I am able to schedule a two-way synch between the FTP server and another cloud provider at MultCloud to be able to access the data. I am able to provide you with the credentials for this server if required for additional troubleshooting.